Flow Cytometric immunophenotyping is a sensitive technique for analysis of benign and malignant tumors. We are studying the refinement of this technique and its application to diagnosis and measurement of prognostic markers in different systems. We are studying the flow cytometric immunophenotype of CLL and correlating the expression of specific antigens with morphology, cytogenetics and clinical course. Data from this study may provide prognostic markers for this disease. We have refined methods for flow cytometric monitoring of patient specimens for apoptosis induced by chemotherapy and have been able to detect apoptosis in specific cell populations. This has allowed us to demonstrate different sensitivities of specific cell lineages to chemotherapeutic agents. We have initiated a study of clonal cytotoxic T-cell populations that arise in patients with B-cell neoplasia to determine prognostic importance as well as resulting difficulties in minimal residual disease detection. As a result, we have found that clonal cytotoxic T-cell proliferations occur with surprising frequency in hairy cell leukemia. The laboratory has an ongoing interest in detection of minimal and residual lymphoma. We are using multiparametric approaches to improve the sensitivity of detection of monoclonal B-cell populations. By targeting abnormal patterns of antigen expression (eg CD10, CD5, CD23, FMC7, or abnormal intensity of antigen expression) by neoplastic B-cells in light chain detection, we are attempting to detect very small numbers of neoplastic B-cells among admixed polyclonal B-cells. The laboratory is studying specific Flow Cytometric markers of various lymphoma sub-groups (e.g. mantle cell lymphoma) to improve diagnostic accuracy. The Flow Cytometry Laboratory is developing methods for Flow Cytometric analysis of comparitive genomic hybridization to detect gene expression in the research and clinical setting. - Fluorescent probes, leukemia, lymphoma,